[nnc] Fix float->bool conversion on cpu (#57798)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57798
Our instruction sequence was just plain wrong, instead of `fcmp une %x, +0.0`
(unordered equal 0.0) we were doing `fcmp uno`, which is just an unordered check
(i.e., is either side NaN).
ghstack-source-id: 128586464
Test Plan: New unit test against the full cross-product of dtypes.
Reviewed By: navahgar
Differential Revision: D28276269
fbshipit-source-id: ba5e59778e07770fb78ef02309f10edde333a800
